According to our TA, quite a few students in the class don't seem to know what a correct Feynman diagram looks like, and draw diagrams that are physically impossible or mislabeled. In the Standard Model, there are not many different diagrams. If we consider vertices, there are only four types of vertices involving fermions. The strong interaction is based on a quark-gluon vertex. Since color is not generally indicated, all the vertices look the same, with the only difference between one and another being the specific quark flavor involved. The electromagnetic interaction vertices all look the same, involving a charged fermion emitting a photon. The weak interaction is slightly more complex, because we have two types of vertices, those involving W^±, which are antiparticles of one another and whose emission or absorption always changes flavor, and those involving Z⁰, which has vertices like those for photon emission. In fact the only difference between emission of a photon versus emission of a Z⁰ is that the coupling constant is different, and while the EM force has infinite range, the Z interaction is basically pointlike because of the Z's enormous mass. Of course charge is conserved at any vertex.  According to the TA, here are some typical student diagrams:

There are obvious problems with the upper diagram. There is no such boson as W⁰, and the actual Z⁰ boson, if that is what is meant,  cannot cause a change of flavor. It does the same things as the photon, γ. Upon absorption, it could not change one quark into another, nor could it change a quark into an antiquark, or vice versa.  [Particles and corresponding antiparticles can annihilate into Z-bosons, of course. To avoid confusion you should draw diagrams in such a way as to clearly distinguish between spacelike and timelike virtual bosons, with time advancing either upward or to the right... your choice.] The errors in the lower diagram should be obvious to you, also.  Emission of a W boson cannot change a quark or antiquark into a lepton.  It can only change flavor WITHIN the categories of quark and lepton.  In other words, it can change one quark into another, or one lepton into another, only.  In every process we have ever seen in nature, charge is conserved.  It's also true that in every process we have ever seen in nature, both baryon number and lepton number are conserved.  There is no known reason for this, since baryon number and lepton number are not, respectively, generators of symmetries.  Also, electron, tauon and muon lepton numbers are individually conserved except in neutrino oscillations.  Here are some examples of correct Feynman diagrams, gleaned from the internet.